Nitrogen dioxide, `NO_(2)` an air pollutant, dissolves in rain-water to form a dilute solution of nitric acid. The equation for the reaction is: `3NO _(2) (g) + H_(2) O(l) to 2HNO _(3) (1) + NO (g)`
Calculate `Delta S ^(@)` for the reaction in `JK^(-1).` The standard entropy of `HNO _(3) (l) , NO (g), NO _(2) (g ) and H _(2)O (l)` are 155.6,210.6,240.5 and 69.96 J `mol^(-1) K^(-1)` respectively.

Options

A. `155.6 jK ^(-1) `
B. `- 155. 6 J K ^(-1)`
C. `269 . 7 JK ^(-1)`
D. `- 269 . 7 JK ^(-1)`

Explanation

The entropy change is given by `Delta S ^(@) = sum S ^(@) `(prducts)`- sumS ^(@)` (reactants)
`= [ 2 S ^(@) ( HNO _(3) (l)) + S ^(@) ( NO (g)) ]- [ 3 S ^(@) (NO _(2) (g)) + S ^(@) (H_(2) O (1)) ]`
Substituting values, we get `Delta S ^(@) = [ 2 mol xx (155.6 J mol ^(-1) K ^(-1)) + mol xx (210 . 6 J mol ^(-1) K ^(-1))]`
`- [ 3 mol xx (240 .5 J mol ^(-1) K ^(-1) ) + 1 mol xx ( 69.96 J mol ^(-1) K ^(-1)) ] ,` Solving , we get `Delta S ^(@) =- 269. 7 JK ^(-1)`